1. Field of the Invention
This invention relates generally to surgical instruments. More specifically, the invention relates to a pedicle probe for use in forming holes in a vertebral pedicle in preparation for pedicle screw insertion.
2. Prior Art
It is sometimes necessary to perform surgery on the spine in order to repair trauma, correct a deformity, or alleviate the effects of disease. Spinal fusion or stabilization is one procedure that may be employed to treat these conditions.
Spinal fusion may be accomplished by insertion of screws into the pedicle to stabilize a spinal segment. The pedicle is a dense, stem-like structure projecting from the posterior of a vertebra, and there are two pedicles per vertebra that connect to other structures. Since the pedicle is the strongest point of attachment of the spine, significant forces can be applied to the spine without failure of the bone-to-metal connection.
To insert pedicle screws, a long, thin, metal probe is inserted through the pedicle and into the vertebral body, forming a hole for reception of the screw. A variety of probes are known in the prior art, including the so-called gear shift pedicle probe and the Fox pedicle probe. The gear shift probe has a round head on its proximal end, whereas the Fox probe has a flat disc-shaped head on its proximal end.
Conventional modalities used to approximate or simulate screw placement are indirect, and include fluoroscopic guidance and frameless stereotactic guidance. Approximations of the pedicle and surrounding vital structures are obtained from a CT scan or MRI done prior to surgery.
Conventional pedicle probes may be straight or curved, and comprise an elongate solid metal shaft with an enlarged hand grip on the proximal end. The probe may have a shaped distal end adapted for forming a hole through the pedicle, or a separate awl or reamer may first be used to form a hole through the pedicle, and the probe then inserted into the cancellous bone of the pedicle and into the vertebral body to develop a path for the screw.
Proper positioning of a conventional probe depends to an extent upon tactile feel. For instance, advancement of the probe should be smooth and consistent. A sudden plunge suggests breaking out of the pedicle laterally, and an increase in resistance indicates abutment against the pedicle or vertebral body cortex.
These conventional modalities require a steep learning curve, and improper or inaccurate manipulation of the probe and placement of the pedicle screw can result in caudal or medial penetration of the pedicle cortex and dural or neural injury.
Currently, there is no direct way to confirm that the hole was made within the pedicle and that the screw will be placed completely inside the pedicle. Surrounding structures can be injured if a portion of the screw is placed outside of the pedicle. There can be nerve root injury, epidural vessel injury, or spinal fluid leakage caused by a misplaced screw.
Accordingly, there is need for a system and method for insertion of pedicle screws which eliminates the guesswork and error-prone modalities of the prior art. In particular, there is need for a system which provides the surgeon with direct confirmation during the surgical procedure that the pedicle probe is in the right position for forming a hole for proper placement of the pedicle screw.